1. Field of the Invention
The present invention relates generally to gas turbine engine, and more specifically to a turbine rotor blade with near wall cooling.
2. Description of the Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98
In a gas turbine engine, such as a large frame heavy-duty industrial gas turbine (IGT) engine, a hot gas stream generated in a combustor is passed through a turbine to produce mechanical work. The turbine includes one or more rows or stages of stator vanes and rotor blades that react with the hot gas stream in a progressively decreasing temperature. The efficiency of the turbine—and therefore the engine—can be increased by passing a higher temperature gas stream into the turbine. However, the turbine inlet temperature is limited to the material properties of the turbine, especially the first stage vanes and blades, and an amount of cooling capability for these first stage airfoils.
The first stage rotor blade and stator vanes are exposed to the highest gas stream temperatures, with the temperature gradually decreasing as the gas stream passes through the turbine stages. The first and second stage airfoils (blades and vanes) must be cooled by passing cooling air through internal cooling passages and discharging the cooling air through film cooling holes to provide a blanket layer of cooling air to protect the hot metal surface from the hot gas stream.
One prior art turbine blade cooling design is shown in FIGS. 1 and 2 which uses near wall radial flow cooling channels formed within the walls of the airfoil. Cooling air flows into each radial flow channel from the bottom and through a number of cooling air resupply holes that connect to a central cavity. Cooling air flows through the radial flow channels to produce near wall cooling of the walls and then discharged through film cooling holes to produce a layer of film air on the external wall surface. In the FIG. 1 blade cooling design, the spanwise and chordwise cooling flow control due to the airfoil external hot gas temperature and pressure variations is difficult to achieve. Surfaces of the airfoil vary in temperature and pressure and therefore require controlled air flow pressure and volume to control metal temperature.